Food product freezing apparatus

ABSTRACT

A continuous conveyor transports food products in, through and out of a rectangular freezing vault containing a blower and a refrigeration coil. The conveying strand is made up of a series of individual plates attached outwardly of the chain connecting the plates and is free to flex in only one direction. Within the vault the conveyor travels about two parallel elongated spiral networks, each including two vertical shafts supporting a stacked array of rotating sprockets. A crossover strand connects the two networks at the base of two adjacent shafts and a second crossover strand connects at the top of the opposite pair of shafts. The top crossover strand is brought outside the vault and there travels about a driving sprocket and an idler forming an outside loop enclosing a work table for performing operations on the products. The outside loop traces out an asymmetrical geometrical figure having two parallel sides, with the driver located at the acute angle formed therein. The driving sprocket can be sized independently of the other sprockets over which the conveying strand travels within the vault. The vault itself is divided into two chambers, one a vestibule through which the products travel as they enter or exit the vault, and serving to isolate the second chamber from the outside air. The second chamber contains the conveyor networks, the blower and refrigeration coil. The cooling is accomplished by circulating the air within the compartment in a direction transverse to the paths over which the conveyor travels. Deflection systems are employed to insure complete distribution and effective cooling of the products. The blowers and refrigeration coil are located above the conveyor networks along substantially the entire length of the conveyor networks.

FIELD OF THE INVENTION

This invention relates in general to machines for freezing food productsand more particularly to such a machine employing a continuouslyoperating conveyor system and a convection cooled freezing vault.

DESCRIPTION OF THE PRIOR ART

Food product freezing machines employing freezing vaults andcontinuously operating conveyor systems are known in the art. In suchsystems the conveyor configuration and the heat transfer characteristicswithin the vault involve interlinked design considerations, since thelength of the conveyor system within the vault is determined by theamount of time, at a given speed, which is required to freeze the foodproduct, while the cooling efficiency within the vault depends on boththe air flow and refrigeration design and the arrangement and theconveyor elements within the vault. In these systems, the food productis deposited on a product carrying plate on the conveyor outside thevault and is then carried by the conveyor into the vault where it isfrozen and thence out of the vault to be picked up by the other foodprocessing machinery. From a cooling efficiency and floor spacestandpoint, the freezing vault should be as small as possible, yet aconsiderable length of conveyor within the vault is required to retainthe product for a sufficient period to freeze it. Accordingly theconveyor strands within the vault follow a circuitous path in order toobtain the necessary time at the selected conveyor speed. Various formsof conveyor path configurations, or stranding, have been employed in theprior art devices. The conveyor itself is usually formed of a rollerchain carrying a series of individual product support plates, fixed toone side of the chain. Since a series of these closely spaced platesallows the conveyor to flex in only one direction, the circuitous pathis free to turn in only one direction, thereby imposing a relativelysevere limitation on the choice of path configurations. Most of theforms of stranding have employed two parallel spiral networks, eachconsisting of two vertically arranged rotatable shafts, with a verticalseries of idler sprockets mounted on each shaft, and a conveying strandbetween the two shafts, the path always turning in the same directionabout each shaft. In one network the strand follows a downward spiralpath and in the other an upward spiral path. The most convenient meansfor connecting the two networks together is by passing a crossoverstrand from the bottom sprocket of one shaft of the downward spiral tothe bottom sprocket of a shaft of the opposite upward spiral, andpassing the second crossover strand from the top sprocket of a shaft inthe first network to the top sprocket of a shaft in the oppositenetwork.

Two configurations of stranding are employed by prior art systems tobring a loop of the conveyor outside the vault. In one arrangement thetop connecting strand passes from one network, beyond the other network,and then through one wall of the vault, where it passes over a drivingsprocket and then runs in a direction parallel to the networks withinthe vault for the length of the vault until it reaches a sprocket stilloutside the vault. The loop turns at this additional sprocket and thenre-enters the vault through the wall to join the other spiral network.In another arrangement one of the loops of a spiral network is broughtout at the short end wall of the vault nearest the shaft it wouldotherwise have turned around to an externally mounted drive sprocketwhere it turns then re-enters through the same wall of the vault andcontinues along the same network. In the first configuration, the chainis only in contact with the driver along a 90° arc. In the latterconfiguration the chain is in contact with the driver along a 180° arc,however the distance between the two sides of the outside loop islimited to the pitch diameters of the idler sprockets within the vault,since the chain can only turn in one direction. In this configurationthen, either the work area is very narrow or the sprockets are quitelarge, the latter condition incurring wasted space within the vault.

In the prior art machines the heat transfer designs have utilized bothconduction cooling and convection cooling. In one prior art conductionsystem, the plates are in direct contact with a refrigerator coil. Inthe convection system, the products are exposed to circulated air whichhas been chilled by passing it over a refrigeration coil. For a givenvault base area and conveyor run-length within the vault, a rectangularbase area with each spiral network aligned with the longer dimension ofthe vault is preferred, since fewer passes from shaft-to-shaft need bemade. In one prior art convention cooling system, the blower is locateddirectly above the conveyor and adjacent the wall containing the passthrough windows for the conveyor. The flow of high velocity air from theblower impinges directly on the conveyor where the conveyor enters thevault, and then passes along the base of the vault, upwardly through theconveying system, and over a refrigeration coil located above theconveying system. This system does not employ any turning vanes toprevent stratification and stagnation of the air within the vault, andaccordingly some portions of the vault receive virtually no aircirculation at all. Furthermore, circulating the air directly at thefood products as they enter the vault produces turbulence in this areawhich results in the loss of cold air through the conveyor pass throughwindows and the infiltration of warm moist air from outside the chamber,thus further reducing the efficiency of heat transfer of the system,particularly since the warm moist air frosts the inside of the chamber.This frost build-up necessitates frequent defrosting production haltsand further reduces efficiency, since it clogs the refrigeration coil.The blower in this prior art device directs the air flow along a pathparallel to the spiral networks. Since it follows the narrower dimensionof the vault, it must travel at a higher velocity, in order to achievethe same volumetric flow rate, as it would if it could follow a broaderstream tube area. Thus when this system operates at the maximumallowable flow velocity to avoid disturbing the products on the plates,the coil must be maintained at a lower temperature level in order toobtain the same cooling rate that could be achieved at this same flowvelocity with larger volumetric flow rate.

SUMMARY OF THE INVENTION

In the present invention the freezing vault is rectangular and includesan internal conveyor configuration of two parallel elongated spiralnetworks, each network including two upright shafts carrying a stackedarray of rotating sprockets. The conveyor roller chain with its attachedproduct carrying plates passes around these sprockets. The top crossoverstrand passes in and out of the vault through openings spaced apart inthe short, end wall, a distance equal to the separation between the twoouter strands of the two spiral networks. Outside the vault this strandpasses over a driving sprocket and an idler and traces out anasymmetrical geometrical figure having two parallel sides with thedriving sprocket located at the corner of the figure containing theacute angle. In this configuration the chain is in contact with thedriver along an arc greater than 90°. Furthermore the driving sprocketin this configuration can be substantially larger than the rotatingidler sprockets over which the conveyor travels within the vault. Withthis arrangement the work table formed by the enclosed area of the loopcan be sufficiently wide so that the product depositing and pick-offdevices can be located within the area formed by the outside loop. Thisconfiguration permits a designer a choice in shape and allows him toselect the optimum length for the outside loop, since the other geometryrestraints that existed in the prior art deivces no longer apply.

The freezing vault is divided into first and second chambers by abulkhead located directly opposite and a short distance from the passthrough wall of the vault. This bulkhead contains openings allowing theconveyor to pass through, as it enters and exits the vault. The firstchamber serves to buffer and isolate the second chamber from the outsideair, while the two spiral networks of the conveying system are locatedwithin the second chamber. A series of fans and a refrigeration coil arelocated directly above the spiral networks and extend the entire lengthof the networks. The fans move the air in a direction perpendicular tothe long axis of the spiral networks onto the refrigeration coilpositioned opposite the fans and extending along the opposite wall ofthe vault. The air then flows down that longitudinal wall and isdeflected back at all levels through the conveyor networks to the sideof the vault where the fans are located. This refrigeratingconfiguration is superior to the air circulation method used in priorart devices, since it permits a larger volumetric flow rate for the sameair velocities. This in turn, permits the coil to operate at a highertemperature and greatly increases the efficiency of the freezing cycle.Moreover the circulation pattern, crosswise of the chamber, does notblow air directly past the pass through windows to the outside, and thusthe amount of air brought into the vault through these windows isreduced.

The larger available refrigeration coil face area has a greatertolerance to frost build-up and blockage and permits the use of a coilthat is thinner in the direction of flow, thereby reducing theresistance to the air as it flows through the coil.

In order to prevent flow stratification and air stagnation, turningvanes are placed at three 90° turn in the flow path. These vanes arelocated in access aisles which extend between the vault walls and theouter sides of the spiral networks. These vanes are hinged to provideready access to the conveying system. Another set of deflection vanesare attached to the conveyor support rails to cause a portion of thecirculating cold air to flow up against the base of the product carryingplates, thereby increasing the rate at which heat is transferred throughthese plates and from the products they carry.

The first chamber or vestibule not only reduces the exchange of air withthe outside atmosphere, but also acts as a dehumidifier by exposing anywarm moist air that enters it to the cold air trapped therein, therebyprecipitating the moisture as frost before it enters the second chamber.

As mentioned above, each spiral network comprises two vertical shaftssupporting a stacked array of rotatable sprockets with the conveyingstrand passing alternately from one shaft to the other until it reachesa point diagonally opposite the point at which it first entered thenetwork, whereupon it passes on to the other network. Each shaft issupported by a supporting frame. In this device the top sprocket on thefar end of the ingoing network is not directly connected to the shaft,to which the other sprockets forming this end of the network areattached. It is attached, instead, to a beam which forms the top side ofa parallelogram linkage. This beam is free to move in a directionparallel to the base of the vault within the plane of linkage, which isparallel to the plane of the ingoing spiral network. Thus upper memberis subject to a continuous force which tends to push it away from theopposite shaft of this network. This linkage keeps the conveying strandsin tension and compensates for any relative dimensional changesdeveloping between the conveyor and the support frame during normaloperation, or as a result of temperature changes occurring when thesystem is shut down or started up. This arrangement greatly reduces thepossibility that the chain will become disengaged from the sprocketsover which it travels. In the described machine an improved efficiencyof the driving mechanism is achieved due to the increased wrap aroundthe driving sprocket, and the fact that the driving sprocket can besized independently of the idler sprockets within the freezing vault.The external loop forms an enclosed area of suitable size and shape formounting devices to perform operations on the product outside freezingvault. The cooling system of this invention operates at a much greaterefficiency and is less susceptible to frost build up and blockage, whilepermitting the maximum use to be made of freezing vault volume.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the drawings in which:

FIG. 1 shows a perspective view of a freezing apparatus in accordancewith this invention;

FIG. 2 is a sectional plan view of a freezing system in accordance withthis invention;

FIG. 3 is a diagrammatic illustration of a stranding configuration inaccordance with this invention;

FIG. 4 is a sectional front view of the freezing vault in accordancewith this invention;

FIG. 5 shows a sectional right side view of a freezing system inaccordance with this invention;

FIG. 6 is another front sectional view of the freezing vault inaccordance with this invention;

FIG. 7 is an enlarged sectional view of a portion of the conveyingsupport frame in accordance with this invention; and

FIG. 8 is an enlarged right side view of the strand tensioning mechanismin accordance with this invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, the external configuration of my food productfreezing apparatus is shown. The endless conveyor 4 carries foodproducts 24 on a series of plates 26 through freezing vault 2. Worktable6 supports conveyor 4, driving sprocket 8 and idler 10. Driving sprocket8 is mounted on a shaft connected to a driving motor (not shown) withinworktable 6. Ice cream extruders 12 and 14 are located within theenclosed area formed by the outside loop of conveyor 4 and vault 2, andare also attached to worktable 6. After the conveyor 4 passes arounddriving sprocket 8, it collects soft food products at either station 12or 14. Stick inserter 16 may be used to insert holding sticks into theproducts as they pass by that station. After the products are depositedon the plates 26 of conveyor 4, they are carried into the freezing vaultthrough pass through window 18. After the products are frozen solidwithin freezing vault 2, they exit through pass through window 20 andare then removed from the conveyor by a pick-off apparatus 22.

The conveying plates 26 are individually and separately mounted inseries on a conveying chain 86 (FIG. 7) and can support either foodproducts 24 or ice cream cone novelties which can be inserted intosupport holes 28.

As illustrated in FIG. 2, the freezing vault 2 is divided into avestibule chamber 30 and a second chamber 32 by bulkhead 34. The outsideloop 60 of conveyor 4 moves through the bulkhead pass through windows 36and 38. Within the second chamber 32, the conveyor 4 passes about twospiral networks 40 and 42. Network 40 is the ingoing network and network42 is the outgoing network. The walls of freezing vault 2 are insulatedto reduce heat transfer from the atmosphere into the vault. Access tothe interior of vault 2 may be had through access doors 52, 54, and 56.

As noted above, the individual plates 26 are each individually andseparately mounted in series on the side of conveying roller chain 86.This arrangement obviously will only permit the conveyor 4 to flex inone direction. In the system shown, where the plates 26 are mounted onthe left side of the chain 86 the conveyor 4 is only capable of flexingto the right. This limitation imposes severe restrictions on the formsof stranding which may be employed. The form of stranding employed inthis device is best illustrated in FIG. 3. The stranding system iscomposed of two parallel spiral networks 40 and 42. Each shaft 44, 46,48 and 50 supports a vertically stacked array of sprockets 62, aroundwhich the conveyor 4 travels. Ingoing network 40 receives the conveyingstrand 4 from idler 10 and passes it, around the sprockets 62 on shafts44 and 46, in a downward traveling spiral until it reaches the lowestsprocket on shaft 44. It then passes as connecting strand 58 to thebottom sprocket on shaft 48 where it enters the upwardly spiraling andoutgoing network 42, passing alternately around the sprocket 62 onshafts 48 and 50 until it reaches the upper most sprocket in network 42where it becomes the top connecting strand 60. This top connectingstrand 60 forms the outside loop which passes through the walls of thefirst chamber 30, as shown in FIG. 2.

Outside the vault 2, loop 60 passes around driver 8 and idler 10. Loop60 encloses a plane forming an asymmetrical geometrical figure havingtwo parallel sides. The driving sprocket 8 is mounted further away fromthe freezing vault 2 than idler 10, and is therefore located in theacute angle formed by the conveying strand 4 as it passes from vault 2around the driver 8 and over to idler 10. Thus the conveyor chain 4 isin contact with driving sprocket 8 along an arc that encompasses anangle substantially greater than 90°. Obviously it is desirable to havea large wrap around the driving sprocket 8, so that it can driveconveyor 4 with less tendency to jump teeth, by taking advantage of moreteeth in contact. In this configuration, driving sprocket 8 can be sizedindependently of the idler sprockets 62 since, loop 60 does not returnfrom it directly to network 42. Hence driving sprocket 8 can be sizedaccording to good driving sprocket practice. The distance between thetwo parallel sides 63 and 64 of loop 60 is equal to the distance betweenthe outside strands of the two networks 40 and 42, which is greater thantwice the width of either network. Thus the enclosed area formed byoutside loop 60 provides sufficient area of a suitable shape to mountthe devices which deposit, operate on, or pick-off the food products asthe conveyor 4 passes outside the freezing vault 2. Additionally thisloop can be sized to keep to a minimum, its exposure time to the warmeroutside air. Most importantly this form of stranding still meets theright-hand turn limitation imposed by the conveyor design.

As shown in FIG. 2, within the vault 2 the second chamber 32 has arectangular plan area. The directions of travel of conveyor 4 innetworks 40 and 42 is aligned with the longer dimension of chamber 32.As shown in FIGS. 4 and 5 the flow of air within this chamber 32 isprovided by a set of fans 66 housed above spiral networks 40 and 42 andpositioned directly opposite a refigeration coil 68. These fans 66extend substantially the entire length of networks 40 and 42.Refrigeration coil 68 also extends the entire length of the networks 40and 42. The exit area of fans 66 and the frontal area of coil 68 aresubstantially equivalent. The flow of air from the fan 66 is directedinto coil 68 where it is chilled and after passing through this coil isdeflected by a first set of turning vanes 70, then proceeds downwardlythrough the chamber until it meets a second set of turning vanes 72where it is deflected horizontally flowing across networks 42 and 40 ofconveyor 4. After this frigid air passes completely through theconveying system within chamber 32, it is deflected upwardly by a thirdset of turning vanes 74 into the intake of fans 66.

Below a maximum coil temperature more efficient freezing is achieved byincreasing the circulation rate of the air through the chamber than canbe achieved by further reducing the coil temperature and maintaining thesame rate of circulation. However, increasing the air flow velocityabove 750-1000 feet per minute does not substantially increase coolingefficiency, thus placing an upper limit on desirable air velocity withinthe chamber. As shown in FIG. 5, the fans 66 occupy substantially theentire area between the uppermost portion of the conveying network andthe roof of chamber 32. Such an arrangement will, at any given air flowvelocity, produce the maximum volumetric flow rate available for thischamber. Given the same freezing chamber size and air velocity, thisarrangement will produce a volumetric flow proportionately greater thanthat produced by prior art devices in which the fans were oriented 90°in the other direction which produces a cross sectional area of flowreduced by the ratio of the width to the length of the chamber for thesame height chamber. At the maximum flow velocity of 750-1000 feet perminute, the refrigeration coil 68 can be maintained at its mostefficient temperature setting. In this arrangement there is a completecirculation of the frigid air through the freezing chamber withoutlosses due to stagnation or stratification of the air as it circulates.

The details of construction of the conveyor are illustrated in FIG. 7,where two opposite levels of the conveying network 42 are shown. Ingeneral the network is formed of a fixed steel frame 92 carrying aseries of support rails 90, forming an elongated spiral track with theproduct plates 26 carried on a flexible roller chain 86 over theserails. As there indicated, the stainless steel support plates 26 arefixed to the roller chain 86. Phenolic wear strips are employed as thesupporting rails 90 to maintain the plates 26 in the horizontal plane.This same material as is used as a rail 100 to guide the chain in thevertical plane operating in conjunction with the face of rail 90.Supporting rails 90, and deflectors 94 and 96 are attached to frame 92by brackets 122. The deflector plates 94 are located upstream of supportframe 92, with respect to the air flow and deflector plates 96 arelocated downstream of the frame. As shown by the flow direction arrows,the deflector plates 94 and 96 tend to scoop the air and cause the airstream, as it passes across the conveyor, to impinge against the base ofthe support plates 26. They may also trip the flow, if it is not alreadyturbulent. These deflector plates substantially increase the heattransfer from the base of plate 26 and thereby substantially reduce thetime it takes to freeze product 24. This arrangement further increasesthe efficiency of the entire freezing system.

As noted above the coil 68 extends substantially the entire length ofnetworks 40 and 42 and has a frontal area approximately equal to theexit area of the series of fans 66. Thus coil 68 can be thinner thanprior art coils, thereby presenting a smaller cross sectional area tothe flow with proportionately less flow impedance. Coil 68 also has aproportionately greater tolerance to frost build-up and blockage, whichwould otherwise rapidly degrade the efficiency of the system.

As shown in FIG. 6, the bulkhead 34 extends from wall to wall and fromthe floor to the ceiling of vault 2. The only openings between the firstchamber or vestibule 30 and the second chamber or air box 32 is throughthe pass through windows 36 and 38 inserted for conveyor 4. The flowpattern produced by the air circulation system 66 and 68 is generallyparallel to the plane of bulkhead 34, thus keeping to a minimum the airexchange between the chambers. Furthermore, as shown by the flowdirectional arrows through windows 36 and 38 in FIG. 2, cold air leakingfrom the second chamber or air box 32 through window 36 tends to returnthrough window 38. The introduction of the bulkhead 34 between thefreezing system and the outside wall of the vault 2, through which theconveyor 4 passes, tends to further isolate the freezing system from theoutside air and decreases the amount of air exchange with theatmosphere. Heat transfer through uninsulated bulkhead 34, and the coldair that does leak into the vestibule 30 tends to keep that chamber at avery low temperature. Accordingly, the outside air that leaks throughpass through windows 14 and 20 into the vestibule 30 is quicklydehumidified, since the temperature of chamber 30 is low enough to causeprecipitation of the moisture contained in the air. This arrangementincreases the operating time between defrosts of the freezing system,since it retards frost build-up within chamber 32. Obviously, the lessoften the system is shut down, the greater its productivity.

In every freezing system of this type, it is necessary to provide accessto the machine in the event of breakdown or for routine inspection.Access aisles 82 and 84, shown in FIG. 4, are provided for that purpose.The turning vanes 70, 72 and 74 are inserted in these aisles and occupywhat would otherwise be wasted space within the vault. These vanes arehinged respectively at 76, 78 and 80 and can be swung out of the waywhen access is desired to the machinery contained within the secondchamber or air box 32.

As shown in FIG. 3, the uppermost sprocket, 100 in network 40 is notdirectly attached to shaft 44. Referring to FIG. 8, sprocket 100 isshown supported by a bearing support mount 118 which is attached to beam102. Beam 102 is pivotally fastened to arms 104 and 106, at pointsequidistant from beam 108 to which they are pivotally attached. Beam 108is fixedly attached to support frame 92. The parallelogram linkage 120formed by these members permits beam 102 to move to the left or right ina direction substantially parallel to beam 108. This linkage is biasedto push beam 102 and sprocket 100 outwardly in order to maintain theroller chain 86 under tension. The biasing mechanism includes shaft 110,guide 112 and spring 114. Shaft 110 is attached to support frame 92 andcarries a guide 112, which is free to travel along shaft 110. Spring 114surrounds shaft 110 and is located between guide 112 and adjustment nut116. Arm 104 is pivotally attached to guide 112. The nut 116 is adjusteduntil spring 114 is compressed and applies a force against arm 104,which in turn pushes beam 102 and sprocket 100 to the right. Chain 86opposes this motion and is thus kept under constant tension. Theparallelogram linkage 120, thereby compensates for relative dimensionalchanges between the support frame and the chain 86, which may be causedby differences in thermal expansion of dissimilar materials orelongation of the chain under load. The parallelogram linkage 120 liesentirely within the conveyor strands 4 as they pass around network 40.The plane of this parallelogram linkage 120 is parallel to the planecontaining shafts 44 and 46 of network 40.

Since certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not interpreted in thelimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, asthe matter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desired to secureby Letters Patent is:
 1. A food freezing apparatus comprising:a vault; acontinuous conveying means for transporting food products into, throughand out of said vault, said conveying means traveling primarily in atleast one network along .Iadd.vertical .Iaddend.substantially parallelplanes within said vault; a refrigeration coil; means for circulatingair in heat exchange with said coil and over said products in adirection substantially parallel to a plane perpendicular to the primaryplanes of travel of said conveying means within said vault; and abulkhead within said vault forming a first and second chamber withinsaid vault, said food products passing into and out of said vaultthrough said first chamber, said second chamber containing said meansfor circulating air, said coil and said networks, wherein said bulkheadis positioned substantially perpendicular to the primary planes oftravel of said conveying means and parallel to said air circulationdirection.
 2. Apparatus in accordance with claim 1 wherein said bulkheadis formed such that the temperature of said second chamber issubstantially lower than the ambient temperature outside said vault. 3.Apparatus in accordance with claim 2 wherein said vault is formed withthermally insulating outside walls and said bulkhead is formed of anon-thermally insulating material.
 4. A food freezing apparatuscomprising:a vault; a continuous conveying means for transporting foodproducts into, through and out of said vault, said conveying meanstraveling primarily in at least one network along .Iadd.vertical.Iaddend.substantially parallel planes within said vault; arefrigeration coil; means for circulating air in heat exchange with saidcoil and over said products in a direction substantially parallel to aplane perpendicular to the primary planes of travel of said conveyingmeans within said vault; and a bulkhead within said vault forming afirst and second chamber within said vault, said food products passinginto and out of said vault through said first chamber, said secondchamber containing said means for circulating air, said coil and saidnetworks, wherein said bulkhead is positioned substantiallyperpendicular to the primary planes of travel of said conveying meansand parallel to said air circulation direction, and further comprising,access aisles within said second chamber, external of said conveyingmeans within said second chamber and running substantially parallel tosaid conveying means; said means for circulating air and said coilextending substantially the length of said networks and located abovesaid networks; said circulating means nearer one corner of said secondchamber; and hinged turning vanes extending substantially the length ofsaid networks located within the other three corners and extending intothe aisles of said chamber.
 5. The apparatus as described in claim 4which further comprises deflecting plates for increasing the heattransfer from the base of said conveying means, said plates directingthe flow of air in said second chamber against the base of saidconveying means.
 6. A food product freezing apparatus comprising:agenerally rectangular freezing vault, cooling means within said vault;continuous conveying means including a series of product carrying platesfor transporting said food products into, through and out of said vault,said conveying means following a circuitous path within said vault, saidpath including a first elongated spiral network and a second elongatedspiral network, the long axis of said spirals being aligned along thelength of said rectangle, each network comprising two stacked arrays ofrotatable members, said arrays being placed parallel to each other andconnected by conveying strands passing alternately from one to theother, said networks being connected at the bottom rotatable members oftwo adjacent arrays by a bottom cross over strand and at the toprotatable members of the opposite two arrays by a top cross over strand,one of said cross over strands passing out of and into said vaultthrough one of the short sides of said vault and forming an outside looppassing around an external rotatable member and encompassing an enclosedarea suitable for placing machinery associated with said freezingapparatus.
 7. The apparatus as described in claim 6 wherein said looppasses around a rotatable driving member substantially larger indiameter than the other rotatable members within said vault.
 8. Theapparatus as described in claim 6 wherein said outside loop passesaround two external rotatable members and forms an asymmetricalgeometrical figure having two parallel sides.
 9. The apparatus asdescribed in claim 6 wherein the external rotatable member, located atthe furthest point from said vault, drives said conveying means.
 10. Theapparatus as described in claim 9 wherein said loop is in contact withsaid external rotatable member along an arc encompassing more than a 90°angle.
 11. Apparatus as described in claim 9 wherein said loop passesaround a rotatable driving member substantially larger in diameter thanthe other rotatable members within said vault.
 12. A food productfreezing apparatus comprising:a generally rectangular freezing vault,convective cooling means and access aisles within said vault; continuousconveying means capable of flexing in only one direction fortransporting said food products into, through and out of said vault,said conveying means traveling primarily along parallel planes withinsaid vault while following a first elongated spiral network and a secondelongated spiral network, the long axis of said spirals being alignedwith the length of said rectangle, each network comprising two stackedarrays of rotatable members, said arrays being placed parallel to eachother and connected by strands passing alternately from one to theother, said networks being connected at the bottom rotatable members oftwo adjacent arrays by a bottom crossover strand and at the toprotatable members of the opposite two arrays by a top cross over strand,one of said crossover strands passing out of and into said chamberthrough one of the short sides of said vault and forming an outside loopencompassing an enclosed area external of said vault suitable forplacing machinery associated with said freezing apparatus; and saidcooling means positioned to direct the flow of air within said vaultalong paths substantially parallel to a plane perpendicular to theprimary planes of travel of said conveying means within said vault. 13.The apparatus as described in claim 12 wherein said cooling meanscomprises an air circulation means and a refrigeration coil.
 14. Theapparatus as described in claim 13 wherein both said circulation meansand said refrigeration coil extend substantially the length of saidnetworks.
 15. The apparatus as described in claim 14 which furthercomprises:a set of turning vanes located within an access aisle withinsaid vault, for turning the air stream from said refrigeration coil todirect it across said conveying means.
 16. The apparatus as described inclaim 15 which further comprises:supporting structure for said conveyingmeans; deflecting means attached to said supporting structure andlocated below said conveying means for directing the airflow toward saidconveying means.
 17. The apparatus as described in claim 12 wherein:said outside loop passes around first and second external rotatablemembers; the first rotatable member, located at a point farther fromsaid vault than the second external rotatable member, drives saidconveying means; said first external rotatable member beingsubstantially larger in diameter than the rotatable members in thearrays within said vault; and said loop is in contact with saidrotatable driving member along an arc encompassing more than a ninetydegree angle.
 18. The apparatus as described in claim 17 wherein saidcooling means comprises an air circulation means and a refrigerationcoil.
 19. The apparatus as described in claim 18 wherein both saidcirculation means and said refrigeration coil extend substantially thelength of said networks.
 20. The apparatus as described in claim 19which further comprises:a set of turning vanes located within an accessaisle within said vault for turning the air stream from saidrefrigeration coil to direct it across said conveying means.
 21. Theapparatus as described in claim 20 which further comprises:supportingstructure for said conveying means; deflecting means attached to saidsupporting structure and located below said conveying means fordirecting the airflow toward said conveying means.
 22. The improvementas described in claim 12 which further comprises:a bulkhead within saidvault forming a first and second chamber within said vault; said oneconnecting strand passing in both directions through said bulkhead andsaid first chamber by means of pass through windows located therein; andwherein said second chamber contains said cooling means.
 23. Theappartus as described in claim 22 wherein said cooling means comprisesan air circulation means and a refrigeration coil.
 24. The apparatus asdescribed in claim 23 wherein both said circulation means and saidrefrigeration coil extend substantially the length of said networks. 25.The apparatus as described in claim 24 which further comprises:a set ofturning vanes located within an access aisle within said second chamberfor turning the air stream from said refrigeration coil to direct itacross said conveying means.
 26. The apparatus as described in claim 25which further comprises:supporting structure for said conveying means;deflecting means attached to said supporting structure and located belowsaid conveying means for directing the airflow toward said conveyingmeans.
 27. The apparatus as described in claim 22 wherein: said outsideloop passes around first and second external rotatable members; thefirst rotatable member, located at a point farther from said vault thanthe second external rotatable member, drives said conveying means; saidfirst external rotatable member being substantially larger in diameterthan the rotatable members in the arrays within said vault; and saidloop is in contact with said rotatable driving member along an arcencompassing more than a ninety degree angle.
 28. The apparatus asdescribed in claim 27 wherein said cooling means comprises an aircirculation means and a refrigeration coil placed downstream of saidcirculation means and upstream of said conveying means.
 29. Theapparatus as described in claim 28 wherein both said circultion meansand said refrigeration coil extend substantially the length of saidnetworks.
 30. The apparatus as described in claim 29 which furthercomprises:a set of turning vanes located within an access aisle withinsaid second chamber for turning the air stream from said refrigerationcoil to direct it across said conveying means.
 31. The apparatus asdescribed in claim 30 wherein said circulating means are located in onecorner of said second chamber and said turning vanes are located in andextend from the other three corners of said second chamber, each of saidvanes extending substantially the length of said networks.
 32. Theapparatus as described in claim 31 wherein said conveying means ismaintained in tension by tensioning means comprising a parallelogramlinkage exerting a continuous force against the top sprocket in thenetwork first receiving said top connecting strand and furthest fromsaid driving means.